This invention relates in general to apparatus for converting a signal from one form to another and more particularly concerns a novel printed circuit balun.
It is often necessary to provide an interface signal matching device between a feedline and a printed circuit dipole antenna. This is generally accomplished by means of a balun, i.e., an unbalanced to balanced signal transformation device inserted in the feed structure. Such devices, when separately constructed of discrete components, add to the cost of the printed circuit antenna devices and increase their overall complexity. These drawbacks, however, can be eliminated if the balun can be formed on as a printed circuit together with the dipole antenna.
In U.S. Pat. No. 3,835,421 issued on Sept. 10, 1974 to DeBrecht et al, there is disclosed a printed circuit balun having some similarities in construction to the present invention. The DeBrecht et al device, however, which is discussed in some detail below, requires a length of conventional wire be soldered between two of its printed circuit conductors and has an inherent 4:1 impedance transformation ratio, as opposed to the inherent 1:1 impedance transformation ratio of the present invention.